Singularity Free Spacetimes -- I :Metric and Fluid Models

Abstract

We show that the metric for the singularity free family of fluid models [3] can be obtained by a simple and natural inhomogenisation and anisotropisation procedure from Friedman--Robertson--Walker metric with negative curvature. The metric is unique for cylindrically symmetric spacetime with metric potentials being separable functions of radial and time coordinates. It turns out that fluid models separate out into two classes, with $\rho \not= \mu p$ in general but $\rho = 3p$ in particular and $\rho = p$. It is shown that in both the cases radial heat flow can be incorporated without disturbing the singularity free character of the spacetime. Further by introducing massless scalar field it is possible to open out a narrow window for $\mu, 4 \geq \mu \geq 3$.